Concrete Materials and Admixtures

Procedure for redosing with superplasticizers

Should you add water when redosing superplasticizers? How much additional mixing is needed after redosing?

There is no requirement to add water when redosing with super. A very small amount of water is often used to wash the super from a bucket or to wash it into the drum of the truck if a dispensing wand isn't used.
Usually, a minimum of 30 additional revolutions is recommended when adding super or any other admixture after the concrete is in the truck. The best way to determine if you've mixed the concrete enough after adding the super is to look at the concrete. After adding super to a load, the remainder of the concrete being discharged ought to have a uniform slump. If the driver discharges the concrete within a reasonable time, the slump shouldn't change significantly during discharge. If there is a slump change, you probably haven't mixed the concrete well enough.